What gives you the idea any military intervention is ever based on protecting a random country's sovereignty? What incentive would NATO or the EU have to join U

What gives you the idea any military intervention is ever based on protecting a random country's sovereignty? What incentive would NATO or the EU have to join Ukraine if this escalates to a direct military confrontation between Ukraine and Russia? Yeah, having Ukraine be annexed by Russia would be a pity but if history has taught us anything a) Russia is too clever to do this without some level of deniability (see the "secession" of the Crimean prior to its annexation) and b) other countries are reluctant to get involved as long as the situation is "self-contained" (i.e. as long as it's just Ukraine and similar post-Soviet states with no direct ties to NATO members or the EU).